Clumped isotope thermometry in bivalve shells: a tool for reconstructing seasonal upwelling

Abstract

Carbonate clumped isotope thermometry is a powerful tool for reconstructing paleotemperature and paleosalinity. Despite its broad application in biotic and abiotic materials, its use in paleoclimate studies has been limited due to the large amount of material and high precision required for each temperature estimate. In addition, it is still uncertain to what extent the clumped isotope signal is modified during calcification in various organisms. Using an analytical approach that minimizes sample size, we analysed clumped isotopes (Δ47) in two bivalve shells from the upwelling-dominated Gulf of Panama to reconstruct seasonal temperature and salinity variations. Using the high-resolution profiles in δ18Oshell, we grouped Δ47 measurements into several intervals to obtain robust average temperature estimates. The reconstructed temperatures agree with available observational data at the 95% confidence level, reflecting seasonal temperature changes of at least ∼6 °C. By combining bivalve δ18Oshell and Δ47-based temperatures, we obtain realistic estimates of seasonal δ18Oseawater and salinity changes. Our results suggest that clumped isotopes in bivalve shells can be used for seasonal temperature reconstructions and for disentangling the temperature and δ18Oseawater signals in δ18Oshell variations.